Asterias amurensis is considered established in Port Phillip Bay. There have been detections of A. amurensis in San Remo, Andersons Inlet, Waratah Bay, Tidal River and the Gippsland Lakes area, however, efforts are made to ensure that they do not establish. The public are encouraged to report suspected detections of A. amurensis in areas outside of Port Phillip Bay.
A. amurensis was introduced into Tasmania in the 1980’s (Buttermore et al., 1994). A. amurensis has been recorded from Banks Strait in the north of the state to Recherche Bay in the south. The highest population densities are found in sheltered bays in south east Tasmania, particularly the Derwent Estuary (DPIPWE, 2015). There have been no recent assessments of A. amurensis populations in Tasmania.
The northern Pacific seastar, Asterias amurensis, occurs naturally on the coasts of Japan, eastern Russia, the Korean Peninsula and is also found in Alaska (Byrne et al. 1997; Davenport and McLoughlin 1993). It has a small central disc with five distinct arms that taper to pointed tips. They commonly range in colours from a uniform pale yellow with purple arm tips to mottled yellow-purple. A. amurensis is relatively large, with fully grown individuals approximately 50 cm in diameter.
A. amurensis is highly invasive and was introduced into Tasmania in the 1980s (Buttermore et al., 1994) and has since spread to Victoria (O’Hara, 1995; Holliday, 2005). Female seastars are capable of releasing 10-25 million eggs per year and the species can therefore undergo massive population growth under optimal conditions. A. amurensis was listed as an Australian pest species of national priority in 2019 (MPSC, 2018) because of its impacts on aquaculture, commercial shellfish industries (Davenport and McLoughlin, 1993; Grannum et al., 1996; Hutson et al., 2005; Ross et al., 2004) and its implications with the population decline of the endangered spotted handfish (Brachionichthys hirsutus) (Bruce and Green, 1998). This species is presently included in Australia’s Priority Marine Pest List.
A. amurensis is typically found in shallow waters particularly within estuaries and on mud, sand, silt or rocky sheltered areas of intertidal zones (CSIRO, 2004).However, the species has been observed in a range of habitats including rocky reefs and bedrock and in its native range has been reported to depths of up to 200m.
A single Asterias amurensis specimen as found in its natural surrounds. The tips of each of its arms pointed upwards.
Asterias amurensis with typical colouration. Colour can vary but usually there is some purple on the tips of arms.
Asterias amurensis diagram & key features. 5 arms with pointed tips, oftern turned upwards. Arms join into central disc. Colours ranges from yellow and orange to purple. Spines irregularly arranged down arms. Single row of spines along groove where tube feet lie, joining fan-like at the mouth.
Four specimens of Asterias amurnensis as found in their natural sorrounds.
Underside of Asterias amurensis showing key features as in the diagram.
Asterias amurensis. Note these individuals are more slender than those in other pictures here. Where food is abundant the seastars can have much thicker arms.
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